After two years of talking, and arguing, about it, the U.S. Army has decided that a major upgrade of the M-1 tank would probably not happen, because this would require some major (and expensive) changes. The money is not there now, and probably not going to be there for 5-10 years, if ever. The army wanted to get the weight (now 62 tons) under 60 tons. This would require something major, like a new turret. This seemed possible because it's been noted that the new French Leclerc tank has a 19 ton turret that offers about the same protection as the current 24 ton M-1A2 turret.
The impressive performance of the U.S. M-1 tank in Iraq prompted the U.S. Army to scrap plans to retire the M-1, and replace it with a radical new FCS (Future Combat System) design. None of the proposed FCS designs showed much potential, especially compared to how well the M-1 was doing. Recently the FCS program was abolished, because it was too expensive, and didn't appear to be going anywhere.
So now there's an M1A3 (or M1E3) version of the M1 in the works. This effort has been under study for over two years. It proposes making the 62 ton M-1A2 a few tons lighter, perhaps installing an autoloader, using new fiber optic wiring, and new (and lighter) armor. A new engine and running gear could also save weight. The M-1E3 might get down to 55 tons, or less.
But the most important changes would be the new computers, communication, sensors and navigation gear intended for the unrealized FCS tank. The FCS vehicle was to use new heavy weapons, that fire guided projectiles to a range of 12 kilometers. These can also be mounted in the M-1E3.
The M-1E3 proposals mean that no new tanks built, just upgrades of existing ones. Nearly 9,000 M-1s were manufactured during the 1980s and 90s. The U.S. Army and Marines only use about 1,600 now, with foreign operators accounting for another 1,500. So there are plenty of older M-1s in storage, ready for upgrading. The M-1E3, or existing M-1A2s, could remain in service for another forty years or more.